Pulsing spray gun

Calling all painters (this does not include me). I have an older Devilblis Finish Line spray gun that used to spray pretty well. Now it pulses and blows bubbles into the paint cup when the trigger is pulled. Everything is very clean, no passages are obstructed, the needle seal seems undamaged and is appropriately tight, the cup is sealed and tight, I've tried two regulators, I've tried various line and gun pressures, all with no success. Any and all help will be appreciated.

Thanks, Chuck

Bubbles from the pickup tube? Indicates to me that something is plugged in the tip somehow, therefore pressurizing the fluid chamber.

I had an old siphon gun with a plugged vent tube that would surge material. Caused a big giant blast of black Centari on an otherwise very nice second coat of a Jeep hood long ago.

(I had gone on a friend's word that it was "clean and ready to go" :dodgy: )

Hi Chuck,

Firstly, is your gun a siphon feed or gravity feed model? In any event this problem revolves around unwanted air leaking into the gun from unwanted places.

In regards to a pulsing or fluttering gun -

Look to a Loose fluid tip.

Fluid tip not seated correctly in gun head.

Gun (with cup) tipped at excessive angle.

Obstructed fluid passage or hose.

Loose or cracked fluid tube in cup or tank.

Insufficient fluid in cup or pressure tank.

Too heavy fluid for suction feed.

Dry or worn packing or loose packing nut.

Plugged vent on suction feed cup.

Gun fluid inlet loose or not sealed/seated correctly.

Fluid hose or cup not fitted correctly to gun fluid inlet connector.

Gun is sucking air around the cup gasket. (siphon feed)

Fluid needle damaged or loose.

Fluid needle not seated or sealing correctly.

Air cap is damaged (off center) and lets air in around the thread.

There may not be enough material in the cup, and if you tip the gun excessively, the siphon tube sucks in air and causes sputtering. The material may be too heavy for the gun. Often there's an obstruction of dried finish somewhere — look for it. Check for a loose fluid nozzle, or a damaged or dirty fluid nozzle seat. A loose or cracked siphon tube may be the culprit. Look for a dried needle packing, or perhaps a loose or defective swivel hex-nut that connects the gun body to the cup.

Fill the cup 1/2 to 2/3 full, and don't over-tip the gun. Back out the needle packing hex-nut and put a drop or two of light oil on the packing (or replace the packing if it can no longer make a seal). Tighten the fluid nozzle, or remove it to clean the contact areas with thinner. Thin material that is too heavy to spray.

In regards to bubbles in the paint pot or cup -

Air leaks. Usually an air leak simply means the air nozzle is loose — tighten its retaining ring. Air leaks also occur if threaded connections are loose. Use Teflon tape on the gun's threaded air input before fastening your hose connector and on the threaded coupling between the gun body and the fluid nipple. Also, obstruction in the gun body fluid passageway causing the pot to become pressurized. A blocked vent hole in the pot lid. Finally, the needle-packing washer may be dry and worn, or the hex-nut cap that tightens the packing may be loose.

Try solving your problems with my tips. If that fails, your gun should be looked at by a professional gun repair company. Get a quote for repairs first, because you may well find your cost to repair and set right you gun problems, is close to or more than a purchase of a new gun. Older, well used and defective guns plus cheaper bought guns tend to be throw away items these days because of the cost of repairs and spare parts.

Hope you solve your problems,

Greg.

Thanks guys for the great replies. It is a first gen HVLP and is mostly constructed of some kind of "plastic". It may be time for a new finish gun.

I'd like to say I'm in the market for an Iwata but, I'm not. I can't justify that kind of money for occasional use. So maybe a Sharpe or Binks or maybe even the famous "purple" gun from Harbor Freight. It seems to have a bit of a following in some circles.

Thanks Again,

Chuck

Thanks guys for the great replies. It is a first gen HVLP and is mostly constructed of some kind of "plastic". It may be time for a new finish gun.

I'd like to say I'm in the market for an Iwata but, I'm not. I can't justify that kind of money for occasional use. So maybe a Sharpe or Binks or maybe even the famous "purple" gun from Harbor Freight. It seems to have a bit of a following in some circles.

Thanks Again,

Chuck

Click to expand...

Yeah Chuck,

It sounds like a new gun is the way to go here. You may remember i put Turtle (Kevin) onto a new sharpe conventional gun. Bang for buck, quality and performance, this gun is a little beauty. BTW - I am not a fan of HVLP guns and don't use them myself unless i can't avoid them.

If you want to check out this particular gun, i can get back to you with a reference connection.

Greg.

Thanks guys for the great replies. It is a first gen HVLP and is mostly constructed of some kind of "plastic". It may be time for a new finish gun.

I'd like to say I'm in the market for an Iwata but, I'm not. I can't justify that kind of money for occasional use. So maybe a Sharpe or Binks or maybe even the famous "purple" gun from Harbor Freight. It seems to have a bit of a following in some circles.

Thanks Again,

Chuck

Click to expand...

Yeah Chuck,

It sounds like a new gun is the way to go here. You may remember i put Turtle (Kevin) onto a new sharpe conventional gun. Bang for buck, quality and performance, this gun is a little beauty. BTW - I am not a fan of HVLP guns and don't use them myself unless i can't avoid them.

If you want to check out this particular gun, i can get back to you with a reference connection.

Greg.

Click to expand...

Now that you bring it up I do remember. I would like the connection. Please educate me on the HVLP vs. conventional pros and cons. I've had some success with another HVLP gun but I have never used a conventional gun.

Many Thanks,

Chuck

OK Chuck,

I'll bring you up to speed on HVLP versus conventional gravity feed production refinish sprayguns. HVLP guns have been around quite a few years now and with their arrival on the refinish scene, they created somewhat of a revolution around the world. Their big claim to fame, lies in two areas. One, they use less material than a conventional spraygun, and two, they create less fumes when you are applying the paint to the surface. By fumes i mean the clouds of atomized paint that are produced when spraying paint, and fill up your spraybooth or room in which you are spraying in. And that's it. That's really all an HVLP gun has over a conventional spraygun. HVLP means high volume low pressure. The concept of a HVLP gun revolves around how the paint you're spraying is atomized through the gun nozzle. HVLP guns atomize the paint differently than conventional guns because the nozzle or setup design allows for more volume of paint to be atomized, but sprayed at a lower air pressure.

It's all to do with the transfer efficiency rate of the paint you're spraying. What is TER. You start with liquid paint in your paint cup, and that paint is to be applied to your panel you're spraying. You want to apply that paint in the most effective way you can from gun cup to panel. You don't want to waste your paint when you are spraying it on by letting it end up in the atmosphere around you, and not on the panel you're spraying. That's what TER is all about. It's getting that paint on your panel, with minimum wastage. HVLP guns have a better TER than conventional sprayguns do, and hence, use less paint material when spraying. That's the big thing that's wowed the refinish world over the years, less paint used, less wastage, and less fume created.

I say, big deal to that. Why? Because i've used both types of gun over the years, and have gotten the same results that ivé talked about above by using my conventional guns. How so you say. It's all about the gun technique or the manner in which you spray your paint on your panel. When HVLP guns arrived on the scene many years ago, spraypainters had to be reeducated in how to spray with them. You have to use a different gun technique wIth an HVLP gun. Firstly, you have to use a much faster stroke speed and secondly, you have to hold the gun at a much closer distance from the surface of the panel you're spraying. These two things are crucial to using the gun. You have to do these things. There are high solid clears and medium solid clears around today in the 2 Pack clear scene. When spraying with an HVLP gun, you can apply i to i 1/2 coats of HS clear, or when using MS clear, i 1/2 to 2 coats of clear is all that's needed. HS clear was brought out to work in conjunction with HVLP guns. When spraying with a conventional gun, i like using MS clear, and i apply 2 coats of that under most situations. Sometimes,i may put on 3 coats when needed for a better film build.

Now here's the thing. These two gun techniques mean that you are going to get a much better TER when aplying your paint, but ever since i started using conventional gravity fed sprayguns many years ago, i myself have used the same gun technique of faster stroke, less trigger pull and closer to the panel, and got the same results as with an HVLP gun, that is less paint used and less fume created. I have proven that the secret lies in gun technique or how you apply the paint to the panel that matters. That's why i come back to and prefer to use a conventional gun over an HVLP gun. I get better film build control, and better flow control, because i use the similar HVLP gun technique of faster stroke and closer to the job with less trigger pull, when i spray. I end up using much less paint and get less fume when spraying. It's all in the gun spraying technique for a better TER. It's well known that the further you hold your spray gun away from the panel, the worse your TER becomes, the closer the better your TER is.

So lastly, have a look at the Sharpe conventional guns. I would be wanting to get a 1.4 setup for basecoat and clearcoat applications. Look at Razor and Finex FX 2000. I think Finex was what Kevin ended up with.

Your references -

http://www.sharpe1.com/sharpe/sharpe.nsf/Page/RAZOR+Conventional

http://www.sharpe1.com/sharpe/sharpe.nsf/Page/Finex+FX2000

Best of luck with it all,

Greg.

Hey Chuck, definitely listen to Greg's recommendation for the Sharpe Finex 2000. Its a very nice gun for the money. It will spray circles around the harbor freight purple gun. I have both. The purple gun can shoot OK but it leaves a ton of orange peel and doesn't lay down very nice. The Finex 2000 made my paint look great, layed down like glass. Seemed to atomize the paint WAY better. I love that gun. I have sprayed a door for a HHR; bed, fender flares, and rockers on my f150; and hood, rockers, rear quarters, and trunk on Taurus. They all turned out great!! I wish I would have had this gun when I shot my nephews Mustang. It would of been a lot less wet sanding for me.

You wont go wrong with the Sharpe for the money.

Thanks for the information Kevin. The info on the Purple gun vs. the Finex is especially helpful. Chuck